Direction: A cylinder is turned on a lathe with orthogonal machining principle. Spindle rotates at 200 rpm. The axial feed rate is 0.25 mm per revolution. Depth of cut is 0.4 mm. The rake angle is 10°. In the analysis it is found that the shear angle is 27.75°.
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In the above problem, the coefficient of friction at the chip tool Interface obtained using Earnest and Merchant theory is
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- 0.18
- 0.36
- 0.71
- 0.98
Correct Option: D
From Earnest and Merchants' theory
2φ + λ – α = 90
where μ = co-efficient of friction = tan λ
∴ λ = 90 + 10 – 2 × 27.75
∴ = 44.5º
μ= tan (44.5)= 0.98
